According to ancient Greek legend, the great warrior, Achilles, was invulnerable against attack, except for one area of weakness—his heel. That weakness would be exploited near the end of the Trojan War by Paris. As the story goes, he shot Achilles in the heel with an arrow, killing his seemingly undefeatable foe.

Okay, so referring to Sola Scriptura as the Protestant Achilles's Heel is not a perfect analogy. There are many weak spots in Protestant...